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Role of Photomasks in Modern Microfabrication
A photomask is an opaque plate with holes and transparent areas that allow light to go through the plate in a specific pattern. Photomasks are widely used in photolithography for the production of integrated circuits, photonic devices, and micro-electro-mechanical systems. Usually, a photomask consists of a fused silica or glass substrate that is coated with an opaque film, into which a replica of the device design pattern is etched. A binary pattern that replicates an original design of the device constitutes the photomask image. This image is used to direct light in a specific pattern, allowing it to ‘print’ the design onto a silicon wafer or another substrate.
Challenges in Photomask Defect Control and Repair Technologies
As photomasks become increasingly smaller, the threshold for potential flaws and defects is also decreasing. The control of pattern defects is the most critical issue in the production of high-end photomasks. The repairs may include carbon patch trimming, sequential defect removal, etc. The leading method of photomask repair has become micromachining, as it is an extremely accurate method of subtractive removal of opaque mask defects. Micromachining utilizes the atomic force microscopy technology.
Micromachining has several advantages, some of which include the ability to machine in tight geometries, high image resolution, the ability to develop custom repair processes, etc.
Optromix – a fiber laser vendor – has developed a custom fiber laser for photomask repair applications. The laser that is used in photomask repair is a fiber DUV laser that replaces an argon-ion laser. Fiber DUV laser provides several advantages over other types of lasers. For instance, a fiber DUV laser does not require a cooler, whereas an argon-ion laser requires a constant supply of running water to cool down. Another advantage is a higher power output, which improves the efficiency of photomask repair. Overall, fiber laser photomask repair has improved significantly through the use of a fiber DUV laser provided by Optromix.
The importance of photomasks and their repair is hard to overestimate. Photomasks are essential in the production of most modern electronics. The photomask repair and upkeep are equally important as they help to improve the quality of production.